1. Technical Field
The present invention relates generally to automotive vehicles and more particularly to an apparatus for coupling two structures together wherein the coupling apparatus spans a variably-sized gap between the structures.
2. Discussion
Mechanical designers are frequently faced with situations wherein a gap is disposed between two structures that are to be fastened together. Often times the gap is variably sized, with the variation in the size of the gap stemming from part-to-part variation between the structures. Regardless of the variability of the size of the gap, its presence between the two structures can be undesirable as it may render the joint more susceptible to flexure. Accordingly, mechanical designers have developed numerous methods for dealing with the presence of gaps between structures that are to be fastened together.
One common technique, particularly in the automotive industry, is employed when the gap is relatively small and one or both of the structures that are to be fastened together are relatively flexible. In these situations, mechanical designers will often utilize the clamping force that is generated by a fastener to deform one or both of the structures to eliminate the gap. One drawback associated with this practice is that the amount of clamping force that is absorbed by the deformation of one or both of the structures is highly variable and not readily quantifiable.
Furthermore, the technique of employing clamping force to deform one or both of the structures is not very well suited where neither of the structures are readily deformable or where the gap between the two structures is relatively large or highly variable in size. In such situations it is frequently a better option to fill the gap with shims or spacers or to employ a strap to span the gap between the two structures rather than to eliminate the gap through the deformation of one or both of the structures.
The use of various sized shims or spacers is typically avoided where ever possible due to the drawbacks that are associated with the fitting of spacers to a particular arrangement. Often times spacers and shims are not easily installed in an application as the position at which they are to be located can be relatively inaccessible. Shims and spacers are also not always sized properly and thereby alter the distribution of clampload through the joint. These errors may stem from an error in the judgment of the technician installing the shim or spacer, or may result simply because while the gap is infinitely variable in size, the technician must choose from a limited number of spacers, each of which are finitely sized. Because of the above-mentioned drawbacks, the use of shims and spacers can be relatively time consuming and costly.
The use of straps also has several drawbacks, including the additional cost associated with the fabrication and installation of the strap and the tendency of the strap to be ineffective in certain types of situations (e.g., in compression). Often times, the single most important factor in determining the suitability of a strap to secure two structures is the ease with which the strap may be installed.
In joining an engine cradle to a vehicle frame rail, for example, the strap may be located at the base of a cylinder block and be relatively inaccessible, particularly where the engine has a V-configuration with a relatively large angle between the banks of the engine (e.g., 90 degrees). In such cases, the banks of the engine prevent a technician from easily accessing the fasteners that secure the strap to the engine cradle and the vehicle frame rails, thereby necessitating the use of relatively complex and fragile low-clearance tooling to install the fasteners. Typically, low-clearance tooling is not durable nor suitable for the transmission of relatively high installation torque""s that are often required in such situations. Consequently, it is frequently necessary to employ a fairly labor-intensive secondary process in such situations wherein the fasteners that retain the strap to the engine cradle and the vehicle frame rail are manually tightened to a predetermined minimum torque.
It is one object of the present invention to provide a coupling apparatus for spanning a gap between two structures and securing the two structures together.
It is another object of the present invention to provide a coupling apparatus that may be easily adjusted to the size of the gap between the two structures.
It is a further object of the present invention to provide a coupling apparatus that accommodates three-dimensional variation between two structures that are to be coupled together.
It is yet another object of the present invention to provide a method for coupling a first structure to a second structure.
In one preferred form, the present invention provides a coupling apparatus for spanning a gap between a first structure and a second structure and fixedly coupling the first and second structures together. The coupling apparatus includes first and second coupling structures, an attachment member and a coupling member. The first coupling structure has an internally threaded cavity and is fixedly coupled to the first structure. The second coupling structure has an externally threaded body and an abutting flange. The externally threaded body threadably engages the internally threaded cavity, permitting the first and second coupling structures to cooperate to span the gap between the first and second structures such that the abutting flange abuts the second structure. The attachment member includes a threaded portion which extends through the first and second coupling structures and threadably engages the coupling member. The attachment member and the coupling member cooperate to generate a clamping force which is transmitted between the first structure, the first and second coupling structures and the second structure to thereby fixedly couple the first and second structures together. A method for fixedly coupling a first structure to a second structure is also provided.